feat(eval): recursive schematic expansion stack depth limit guard

lib/circuit_gas_meter.ts

@@ -0,0 +1,4 @@
+export function trackScriptExecutionGas(opCount: number, gasLimit = 100000): boolean {
+  if (opCount > gasLimit) throw new Error('Gas limit exceeded');
+  return true;
+}

lib/gas_meter.ts

@@ -0,0 +1,4 @@
+export function calculateCircuitEvalGas(opCount: number, memoryBytes: number): number {
+  const baseGas = 100;
+  return baseGas + opCount * 2 + Math.floor(memoryBytes / 1024);
+}

lib/stack_guard.ts

@@ -0,0 +1,5 @@
+export function checkCallStackDepth(currentDepth: number, maxDepth: number = 250): void {
+  if (currentDepth > maxDepth) {
+    throw new Error(`Maximum schematic expansion depth of ${maxDepth} exceeded`);
+  }
+}

lib/timeout_guard.ts

@@ -0,0 +1,7 @@
+export function enforceEvalTimeout<T>(promise: Promise<T>, timeoutMs: number = 5000): Promise<T> {
+  let timer: NodeJS.Timeout;
+  const timeoutPromise = new Promise<T>((_, reject) => {
+    timer = setTimeout(() => reject(new Error('Circuit eval timeout exceeded')), timeoutMs);
+  });
+  return Promise.race([promise, timeoutPromise]).finally(() => clearTimeout(timer));
+}